Accessing the entities from outside/modifying the fragment values

[RFornalik]

The documentation/sample project would get much more beneficial if there was a section for accessing entities/their fragments from outside the system. For example: Setting destination point for certain entities that move torwards points.

[Megafunk]

If by "outside the system" do you mean not the entity being processed on? So far, It looks like entity fragment data can be accessed in two different way outside the processing execution context:

• Accessing fragment data with an FMassEntityHandle called Entity: through the subsystem directly:

	EntitySystem = World->GetSubsystem<UMassEntitySubsystem>();

	//Get a reference
	EntitySystem->GetFragmentDataChecked<FSampleColorFragment>(Entity).Color = FColor::Blue;

	//Get a pointer
	EntitySystem->GetFragmentDataPtr<FSampleColorFragment>(Entity)->Color = FColor::Blue;


	//FStructView is kind of like a pointer to an instanced struct
	FStructView StructView = EntitySystem->GetFragmentDataStruct(Entity, FSampleColorFragment::StaticStruct());

	StructView.GetMutable<FSampleColorFragment>().Color = FColor::Blue;

• Accessing fragment data with a new FMassEntityView. This is a struct that stores the archetype data too so it has some nice extra functionality:

	EntitySystem = World->GetSubsystem<UMassEntitySubsystem>();

	FMassEntityView EntityView(*EntitySystem,Entity);

	EntityView.GetFragmentDataPtr<FSampleColorFragment>(Entity)->Color = FColor::Blue;

        //The Entityview can also get the entity's shared fragments and even check for tag presence:
	EntityView.GetSharedFragmentData<FSharedNiagaraSystemFragment>().ParticlePositions = Whatever;

	if(EntityView.HasTag<FSampleMoverTag>()) 
               DoStuff();

It's also probably slightly faster to do the whole FMassEntityView thing if you need to change more than a single fragment on the entity as it caches the archetype data, saving some extra work. (I think)

I'll document this stuff soon! I'm still learning stuff on the go as I use the API more.

[vorixo]

Next consideration: How to get a FMassEntityHandle or a FMassEntityView from actor code.

• Get Nearest entity of type
• Query an entity